1. Field of the Invention
This invention relates generally to electric energy meters with time-of-day multifunction registers, and more specifically, to the placement of the multifunction register within the meter assembly.
2. Description of the Prior Art
Due to recent escalating costs of generating electrical energy, utility companies and manufacturers of electrical energy metering systems have developed devices to provide for more efficient use of electrical generation facilities during both on-peak and off-peak load periods. One such device, the time-of-day (TOD) meter, measures electrical energy consumption during several time intervals of each day. In this way, a different billing rate can be applied for the electrical energy consumed during each time interval. In the absence of such a multiple rate pricing structure, the low demand usage customer billed at the same rate as the high demand usage customer in effect subsidizes the high demand user. From a customer's standpoint, differential pricing is therefore more equitable. From the utility's standpoint, a multiple rate pricing structure encourages consumers of electrical energy to shift consumption from on-peak periods to off-peak periods, thus increasing the overall power distribution system efficiency and reducing the capital expenditures otherwise required for extra power generating equipment during on-peak periods.
Some meters of the TOD type utilize an induction watthour meter movement with multi-dial registers and gear trains, and mechanical means for selectively engaging separate register dials under the control of a mechanical clock mechanism. The recent application of solid-state electronic devices to TOD meters has eliminated the mechanical registers and gear trains, permitting an increase in the number of electrical energy parameters that can be measured. This has resulted in greater flexibility to the utility regarding the number and application of rate selection sehedules. One such solid-state TOD meter is disclosed in U.S. Pat. No. 4,283,772 which is assigned to the assignee of the present invention. This patent discloses a programmable time registering AC electric energy meter including solid-state logic circuitry with a programmed sequence of operation. The solid-state logic circuitry is referred to as a time-of-day (TOD) multifunction register. Within the TOD multifunction register a first read-write memory device stores energy consumption data (i.e., kilowatt hours and kilowatt demand) in different accumulators dependent upon whether the energy is consumed during an on-peak, off-peak, or intermediate-peak load period. A second read-write memory device stores fixed control point data indicating the on-peak, off-peak, and intermediate-peak periods of each day. Data in the second read-write memory is stored with a minutes, hours, days of the week, and day of the year format. A control unit compares the current real time with the contents of the second read-write memory and controls the first read-write memory such that it accumulates energy consumption data in the on-peak accumulator during on-peak periods, in the intermediate peak accumulator during intermediate peak periods, and in the off-peak accumulator during off-peak intervals. These three load periods correspond, respectively, to the high, mid, and base billing rate categories. The time and date data and each of the time related parameters of kilowatt hours and kilowatt demand are sequentially applied to an optoelectronic readout display of the meter. The optoelectronic display of this meter sequentially shows time in hours and minutes, the day of the week, and the day of the year. It also displays the following accumulated electric energy consumption parameters: total kilowatt hours; kilowatt hours for the high rate, mid-rate, and base rate; and kilowatt demand for the high rate, mid-rate, and base rate.
An optical data link tube, connected to the TOD multifunction register is disclosed in U.S. Pat. No. 4,298,839 which is assigned to the assignee of the present invention. The optical data link tube communicates with an external programmer/reader unit via a plurality of opto-electronic devices to initialize, reprogram, and read the time and consumption data stored in the various read-write memory devices of the TOD multifunction register. The programmer/reader unit is also utilized to perform various data verification and synchronization functions. Further information regarding the programmer/reader unit can be found in U.S. Pat. No. 4,291,375 which is assigned to the assignee of the present invention.
In the aforementioned U.S. Pat. No. 4,298,839 the optical data link tube is mounted on the printed circuit boards carrying the time-of day multifunction register. These printed circuit boards are supported by the meter frame; the meter frame and cover are mounted to the meter base. Proper alignment between the programmer/reader probe and the optical data link tube is facilitated by three finger-like projections located in the front face of the probe. These projections engage three recesses in the meter cover to align the probe with the optical data link tube. Because the optical data link tube is ultimately attached to the meter base and the recesses for aligning the probe with the tube are in the meter cover, any misalignment between the meter cover and the meter base will cause misalignment between the probe and the optical data link tube. Obviously, such misalignment degrades communication between the probe and the optical data link tube. The tolerance build-up associated with attaching the TOD multifunction register circuit boards to the frame and the optical data link tube to the circuit boards also adversely affects alignment between the optical data link tube and the programmer/reader probe. Mounting the TOD multifunction register circuit boards on the inside front face of the meter cover, as disclosed by the present invention, will decrease the tolerance buildup and completely eliminate the detrimental effect on the probe/tube alignment of angular misalignment between the meter cover and base.
Canadian Pat. No. 1,330,076 issued to Landis and Gyr AG discloses a light-emitting device arranged behind the transparent portion of a watthour meter cover. The light-emitting device is embedded in a holding magnet attached to the meter cover. Alignment with an external light-receiving device is facilitated by attraction between the holding magnet and a second magnet located within the light-receiving device. This prior art patent does not disclose recesses in the meter cover or fingerlike projections in the external light-receiving device for aligning the light receiver with the light emitter. Nor does it disclose attaching the light-emitting device to the meter cover as does the present invention.
Heat generated in prior art TOD meters, especially from self-heating of the electromagnet and the ambient temperature, has a deleterious effect on the printed circuit boards and electronic components of the TOD multifunction register. To overcome this problem it is common to paint the meter cover white on the outside. In the present invention the TOD multifunction register is shielded from the other meter components thereby obviating painting the meter cover. This and other advantages of the present invention are discussed in detail below in the "Description of the Preferred Embodiment".